Altruism, as represented in the phenomenon of "helpers", will be studied in a communally breeding species, the Mexican Jay. Helping will be correlated with geneology of individuals barded as nestlings and with knowledge of degree of inbreeding and genetic relationship. The development of helping will be correlated with the ages and sexes and flock members by means of known-age color-barded individuals. The age-structure and geneology of Mexican Jay flocks will be characterized and related to theories about the ecology and adaptive basis for the evolution of altruism.